Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$59.84	4.356%	$62.4466	$62.45	$62.45	$62.40
Purchase #2	$113.36	3.641%	$117.4874	$117.49	$117.50	$117.50
Purchase #3	$50.61	8.556%	$54.9402	$54.94	$54.95	$54.90
Purchase #4	$45.80	3.722%	$47.5047	$47.50	$47.50	$47.50
Purchase #5	$11.37	12.459%	$12.7866	$12.79	$12.80	$12.80
Purchase #6	$54.29	5.335%	$57.1864	$57.19	$57.20	$57.20
Purchase #7	$217.27	11.782%	$242.8688	$242.87	$242.85	$242.90
7 purchase totals =	$552.54		$595.2207	$595.23	$595.25	$595.20